Tunable Metasurface Based on Plasmonic Quasi Bound State in the Continuum Driven by Metallic Quantum Wells

Effectual free-space optical metasurface is essential for telecommunication and information processing. However, the lack of efficient optical nonlinearity is still an obstacle to empower its full capability and practical applications. Metallic quantum wells (MQWs) with large nonlinear susceptibility may pave a new way. Here, such MQWs are implemented into a resonance configuration of the quasi bound state in the continuum (BIC) and an efficient tunable plasmonic metasurface is proposed. Such metasurface is composed of MQWs-based nanostructure, which supports the tunable plasmonic quasi-BIC. The tunability is controlled through substantial change in refractive index of MQWs induced by Kerr-type nonlinearity, which leads to around 9 dB extinction ratio and extremely high modulation speed up to terahertz level. The quasi-BIC with narrow linewidth is obtained through symmetry-breaking of nanoelliptical elements, further enhancing the modulation depth. This work satisfies the ultrafast-speed and high-efficiency requirement of free-space all-optical metasurfaces, including the spatial light modulators in optical computing field.

Automated summary

Effective free-space optical metasurface is crucial for telecommunication and information processing, but the lack of efficient optical nonlinearity remains a challenge for its full potential and practical applications. Metallic quantum wells (MQWs) with high nonlinear susceptibility offer a new solution. In this study, MQWs are incorporated into a resonance configuration of quasi bound state in the continuum (BIC) to propose an efficient tunable plasmonic metasurface. The metasurface, composed of MQWs-based nanostructure, supports tunable plasmonic quasi-BIC, achieving an extinction ratio of around 9 dB and an extremely high modulation speed up to the terahertz level. The narrow linewidth quasi-BIC is obtained by breaking the symmetry of nanoelliptical elements, further enhancing the modulation depth. This work meets the requirements of high-speed and high-efficiency free-space all-optical metasurfaces, including spatial light modulators in optical computing field.